Fuel burning apparatus



Nov. 25, 1958 KARL .HE IlNZ KUPPERS 2,861,526

FUEL BURNING APPARATUS 2 Sheets-Sheet 1 Filed Nov. 19, 1952 u u iifllfll n u u u n i' i u INVENTOR Jfii 7'5 J /emz ppe ATTORNEY #2. Owl

m ATTORNEY 2 Sheets-Sheet 2 INVENT OR ffarl 7 /61 222 K uppersKARL-HEINZ KUPPERS FUEL BURNING APPARATUS Nov. 25, 1958 Filed Nov. 19,1952 United States Patent FUEL BURNING APPARATUS Karl-Heinz Kiippers,(Bberhausen, Germany, assignor to- The Babcock & Wilcox Company, NewYork, N. Y., a corporation of New Jersey Application November 19, 1952,Serial No. 321,383

9 Claims. (Cl. 110'28) The present invention relates to an improvedmethod of and means for burning ash containing solid fuels and moreparticularly to the construction and operation of a fuel burning furnaceadapted for use as the firing means of an associated vapor generatingunit. The furnace provides a combustion chamber within which pulverizedfuel and air are caused to follow a curvilinear path of generallyU-shaped formation throughout the width of the chamber, in contact withthe walls of the chamber, with provision for effecting recirculation offuel and air within the return bend portion of the path. Combustion ofthe fuel is effected under conditions which result in furnace chambertemperatures above the ash fusing temperature whereby the residual ashis rendered available for removal from the furnace as molten slag. Asthe combustion proceeds, the slag is discharged from the chamber inliquid form in a downward direction while the hot gaseous products ofcombustion are discharged from the chamber in an upward direction. Thedischarging gases are caused to pass through a narrow opening whichextends substantially throughout the width of the chamber and then,substantially without change in direction, are caused to flow through atransition passage of progressively increasing cross section directlyinto the radiant heat absorption chamber of the associated unit. Inpulverized fuel-fired furnaces heretofore known, provision has been madefor causing the burning fuel to follow a generally U-shaped path throughthe combustion space. With such furnaces, the combustion chamber hasbeen arranged either to open directly into the radiation space of anassociated vapor generator, or else there has been provided a slagscreen formed of tubes between which the gases would reverse theirdirection of flow be- Xfore continuing into the radiation space.However, in the operation of such furnaces, the U-shaped flame of theEpurning fuel-air stream remains slightly spaced from the furnaceboundaries because it seeks to enter the combustion chamber outlet overthe shortest path. According to the present invention, this is preventedin that the combustion chamber gas outlet is formed as a narrow slotwhich extends substantially throughout the total width of the combustionchamber. The provision of an outlet of such form and dimensions resultsin a higher pressure tlrop into the succeeding radiation chamber than iscustomary and causes the stream of flaming gases to spread throughoutthe interior combustion chamber space and thus fill the total crosssectional area of the gas outlet slot. In order to regain the energyexpended in effecting a restriction of the discharging gas stream, thebody of gases is conducted without substantial change in directionthrough a widening transition passage into a radiation space. Thus, witha furnace incorporating these fea- 'tures, the combustion chamber may bemade as large as may be desired and further a plurality of combustionchambers may be arranged to discharge into a common radiation chamber.Ihe various features of novelty which characterize my r 2,861,526 ICPatented Nov. 25, 1958 invention are pointed out with particularity inthe claims annexed to and forming a part of this specification. For abetter understanding of the invention, its operating advantagesandspecific objects attained by its use, reference should be had to theaccompanying drawings and descriptive matter in which I have illustratedand described a preferred embodiment of my invention.

of the drawings;

Fig. 1 is a secitonal elevational view of a furnace embodying myinvention and arranged as the firing means of a vapor generating unit;

Fig. 2 is a sectional plan view of the furnace shown in Fig. 1, takenalong line 22;

Fig. 3 is a sectional elevational view of a modified vapor generatorfurnace; and

Fig. 4 is a sectional elevational view of Fig. 3, taken along line 4-4.

In more detail, as shown in Figs. .1 and 2, a combustion chamber A ofsubstantially circular cross section is provided within a furnace 2 of.generally circular cylindrical form about a horizontally extendingcentral axis. The circumferential furnace wall 3 and transverse parallelend walls 4, 4 are formed in known manner with fluid conducting tubes 5which are extended upwardly along adjoining walls of the associatedvapor generating section which is located directly above. The tubes 5may suitably be provided at the furnace side with studs welded thereto,and with a covering layer of heat refractory material, while at theouter side of the tubes a covering layer of heat insulating material maybe provided, together with an air tight sheet metal jacket, the detailsof which known wall components are not illustrated. A fluent mixture ofpulverized coal and air is directed into chamber A through nozzles 6,and secondary air through nozzles 7, all of which enter through wall 3adjacent the uppermost part of the chamber, and furthermore are pointedin such a direction that they produce within the cylindrical chamber A arotating flame as diagrammati cally indicated. As shown herein, eachfuel-air nozzle 6 is positioned between two secondary air nozzles 7 in acommon transverse vertical plane, with each fuel air.

nozzle 6 discharging downwardly and vertically, whereas the secondaryair nozzles 7 at opposite sides discharge downwardly in convergingrelation to nozzle 6. The nozzles 6 and 7 are further arranged inlongitudinally spaced groups, as seen in Fig. 2.

Tertiary air is directed into chamber A through nozzles 8 which aredistributed throughout the width of the chamber in two horizontal rowsadjacent the bottom of the chamber, the nozzles 8 extending horizontallyand opening into the chamber at an angle of about to the direction inwhich the primary air-fuel mixture is admitted through nozzles 6. Othernozzles 9 are positioned in the opposite side wall of chamber A so as toprovide quaternary air as'may be required, the nozzles 9 opening intothe chamber at approximately the same elevation as nozzles 6 anddischarging in an inclined downward direction so as to conform to therotational movement of the flame.

The furnace is dimensioned in such a way that at full load, and at thepermissible partial loads, the slag in the combustion space A is liquid.Accordingly, at the lowermost part of chamber A, portions 12, 13 of wall3 at opposite sides of the chamber are spaced apart so as to provide aslag outlet opening or slot 14 extending longitudinally of the chamber,suitably throughout the width thereof between planar end walls 4, 4. Thewall portion 12, including portions of tubes 5, conforms to the circularcurvature of the chamber wall 3, whereas the wall portion 13 is extendeddownwardly in tangential relation to the curved portion of wall 3 soasto be overlapped by the wall portion "'12 inthe direction of flamerotation, thereby'permitting the-molten-slag to discharge through theopening 14 while the fine fuel particles remained entrained in thewhirling fuel-air mixture, The slag outlet slot 14 opens -into-ashaft*-1'5 through-which the-slag is discharged 'below the level'ofliquid in a trough, not shown, whereby a gas seal is provided.

' At'the topof-chamber A, toward the'side opposite=the location offuel-air nozzlesfi,there is 'formed'an-upper gas'outlet 16 which at thisparticular location, in-relation to nozzles 6, permits a 'portion of thecombustion gases to return into the circuit of the whirling-body of fueland air and-thereby contribute to the ignition ofthe fuel. The :gasoutlet 16, which=extendsthroughout the-width of the chamber, isrelatively narrow so asto-pr'ovide sufficient' restriction to thedischarge of gases therethr'ough to cause the combustion gasesto-continuously fill the total interior chamber space A. The gaseousproducts of combustion pass upwardly through the outlet slot .16 into :atransition passage 1-7 of progressively increasing cross sectionparallel to end walls 4, 4 whence the gases are directed intotheiadjoining radiation space '18 from which the gases are furtherdirected into contact with convection heating surfaces, not shown. Thewalls 3 and 4 of chamber A, together with the tubestherein, -areextended upwardly as indicated to :form the corresponding fluid cooledwalls of the transition-passage 17, and the radiation .chamber 18, withtubes of the respective wallshavingilower ends connected to fluidsupplyheaders as shown.

In the modification illustrated in Figs. 3 and 4, the vfurnace20 isformed in general as a hollow right prism of substantially equilateralformation providing a combustion chamber B, the furnace having opposingupright side walls 21, 23 arranged at rightangles to upright end --walls24, 24, all of which walls include fluid conducting tubes as indicated.The upper furnace wall 25 is inclined upwardly toward the front wall 21for a distance greater than one-half of the distance between side walls21, 23 where it is formed with a rounded arch nose portion 26 which,with the front wall 21, defines a relatively narrow rectangular slot 27through which gases are discharged from the combustion chamber B into aprogressively widening transition passage 28, and thence into aradiation chamber 29 of increased rectangular horizontal tcrosssection.The front wall 21 is formed with a reentrant upper portion 31 arrangedparallel to the inclined upper rear wall portion 32. The bottom wall isformed with oppositely rinclined floor portions 34, 34 convergingdownwardly in symmetrical arrangement towarda central -.area in which aslag outlet 35 is formed, spaced from all lateral walls of the chamber.The primary air-fuel streams are directed horizontally past the gasoutlet 27 .into an upper portion of chamber B through nozzles 36 whichare positioned in front wall 21 subjacent the gas 1 outlet. Secondaryair is introduced through nozzles 37 @which, in the same wall, arearranged at opposite inclinations to the horizontal, above and belownozzles 36, so as to provide air streams directed in converging rela-.tion to the primary air-fuel streams. Tertiary air is introduceddownwardly through a row of nozzles 41, adjacent the opposite side wall23, and quaternary air through a row of nozzles 42, all arranged todischarge in the direction of rotational movement of thefuel-.airmixture within the chamber, as in the embodiment hereinbeforedescribed. vAs a .means contributing to the maintenance .of suchrotational movement, the gas outlet slot 27 is traversed at intervals bybridges or tube panels which are formed by groups of alternate wallcooling tubes 5 :of opposing wall portions 21 and 32, with refractorymaterial. covering the tubes and filling the spaces therebetween. Thebridges 45 are desirably inclined across .the ,slot 27' as indicatedlinFig. *3 and furthermore are positioned over the respective groups offuel and air ports 36 and-37 as shown inFig, 4.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of the invention may sometimes be used to advantage without acorresponding use of other features.

I claim:

1. Apparatus for burning particle-formsolid fuelcomprising wall meansforming .an elongated combustion chamber of generally symmetricaltransverse cross-section arranged with its longitudinal axissubstantially horizontal, said wall means having an inner exposedrefractory surface and fluid heating tubes proportioned for themaintenance of said refractory surface under a normal mean temperaturein said combustion chamber above the'fuel ash fusion temperature, meansforming a longitudinally extending greatlyrestricted slot-like gasoutlet in the upper portion of said'combustion chamber, said gas outletbeing proportioned so that a predominant portion of the radiant heatenergy emitted within said combustion chamber will be absorbed thereinand that the pressure drop of the gases flowing through said outlet willbe suflicient to assure uniform distribution of the gases along thewalls of the combustion chamber, means forming a restricted slag outletin the lower portion of said combustion chamber'for the continuousdischarge of molten slag, and means for introducing combustion airand-particle-form solid fuel in suspension into said combustion chambertangentially to an imaginary horizontally disposedcylinder in saidcombustion chamber and effecting -a whirling path of fuel-air traveltherein along and in sweeping relation with substantially the entireinner surfaces of the walls of said combustion chamber and the slagoutlet thereof to cause continuous discharge of some of the gasesthrough the gas outlet and recirculation of some of the gases in thewhirling path to enhance the ignition of the incoming fuel.

2. Apparatus for burning particle-form solid fuel comprising wall meansforming an elongated combustion chamber of generally symmetricaltransverse crossoutlet in the upper portion of said combustion chambersaid gas outlet being proportioned so that apredominamt portion of theradiant heat energy emitted with saitd combustion chamber will 'beabsorbed therein and that the pressure drop of the gases flowing throughsaid outlet will be sufficient to assure uniform distribution of thegases along the walls of the combustion chamber, means forming arestricted slag outlet in the lower pot:- tionof said combustion chamberfor the continuous discharge of molten slag, and means for introducingconnbustion air and particle-form solid fuel in suspension .into theupper portion of said combustion chamber tangentially to an imaginaryhorizontally disposed cylinder in said combustion chamber and eflectinga whirling path of fuel-air travel therein along and in sweepingrelation with substantially the entire inner surfaces of the walls ofsaid combustion chamber and the slag outlet thereof to cause continuousdischarge of some of the gases through the gas outlet and recirculationof some of the gases in the whirling path to enhance the ignition of theincoming fuel, said .last named means including a series oflongitudinally spaced fuel inlets disposed at one side of and adjacentto said gas outlet, and additional air inlets arranged to direct airstreams into said combustion. chamber tangent to said imaginary cylinderat positions downstream from said fuel inlets and in directionspromoting the whirling motion of the burning fuel-air mixture.

3. Apparatus for burning particle-form solid fuel comprising wall meansforming an elongated combustion chamber of generally symmetricaltransverse crosssection arranged with its longitudinal axissubstantially horizontal, said wall means having an inner exposedrefractory surface and fluid heating tubes proportioned for themaintenance of said refractory surface under a normal mean temperaturein said combustion chamber above the fuel ash fusion temperature, meansforming a longitudinally extending greatly restricted slot-like gasoutlet in the upper portion of said combustion chamber, said gas outletbeing proportioned so that a predominant portion of the radiant heatenergy emitted within said combustion chamber will be absorbed thereinand that the pressure drop of the gases flowing through said outlet willbe sufiicient to assure uniform distribution of the gases along thewalls of the combustion chamber, means formin a restricted slag outletin the lower portion of said combustion chamber for the continuousdischarge of molten slag, and means for introducing combustion air andparticle-form solid fuel in suspension into the upper portion of saidcombustion chamber tangentially to an imaginary horizontally disposedcylinder in said combustion chamber and effecting a whirling path offuel-air travel therein along and in sweeping relation withsubstantially the entire inner surfaces of the walls of said combustionchamber and the slag outlet thereof to cause continuous discharge ofsome of the gases through the gas outlet and recirculation of some ofthe gases in the whirling path to enhance the ignition of the incomingfuel, said last named means including a series of longitudinally spacedfuel inlets disposed at one side of and adjacent to said gas outlet, andadditional air inlets arranged to direct air streams into saidcombustion chamber tangent to said imaginary cylinder at positionsdownstream from said fuel inlets and in directions promoting thewhirling motion of the burning fuel-air mixture.

4. Apparatus for burning particle-form solid fuel comprising wall meansforming an elongated combustion chamber of generally symmetricaltransverse crosssection arranged with its longitudinal axissubstantially horizontal, said wall means having an inner exposedrefractory surface and fluid heating tubes proportioned for themaintenance of said refractory surface under a normal mean temperaturein said combustion chamber above the fuel ash fusion temperature, meansforming a longitudinally extending greatly restricted slot-like gasoutlet in the upper portion of said combustion chamber, said gas outletbeing proportioned so that a predominant :portion of the radiant heatenergy emitted with said cornbustion chamber will be absorbed thereinand that the pressure drop of the gases flowing through said outlet willbe sufficient to assure uniform distribution of the gases along thewalls of the combustion chamber, means forming a restricted slag outletin the lower portion of of molten slag, and means for introducingcombustion said combustion chamber for the continuous discharge,

a air and particle-form solid fuel in suspension into the upper portionof said combustion chamber tangentially to an imaginary horizontallydisposed cylinder in said I combustion chamber and effecting a whirlingpath of fuel-air travel therein along and in sweeping relation withsubstantially the entire inner surfaces of the walls of said combustionchamber and the slag outlet thereof to cause continuous discharge ofsome of the gases through the gas outlet and recirculation of some ofthe gases in the whirling path to enhance the ignition of the incomingfuel, said last named means including a series of longitudinally spacedfuel inlets disposed at one side of and adjacent to said gas outlet,auxiliary air inlets disposed adjacent said fuel inlets and arranged to6 introduce air into the upper portion of said chamber in the samedirection as and in impinging relation with the fuel stream, andadditional air inlets arranged to direct air streams into saidcombustion chamber tangent to said imaginary cylinder at positionsdownstream from said fuel inlets and in directions. promoting thewhirling motion of the burning fuel-air mixture.

5. In a fluid heating unit, in combination, wall means defining avertically elongated furnace having an upper radiant chamber and a lowerhorizontally elongated combustion chamber of generally symmetricaltransverse cross-section about its longitudinal axis, the portion of thewall means defining said combustion chamber having an inner exposedrefractory surface and fluid heating tubes proportioned for themaintenance of said refractory surface under a normal mean temperaturein said combustion chamber above the fuel ash fusion temperature, meansforming a longitudinally extending greatly restricted slot-like gasoutlet in the upper portion of said combustion chamber dividing saidfurnace into said combustion and radiant chambers, said gas outlet beingproportioned so that a predominant portion of the radiant heat energyemitted within said combustion chamber will be absorbed therein and thatthe pressure drop of the gases flowing through said outlet will besufficient to assure uniform distribution of the gases along the walls,of the combustion chamber, means forming a restricted slag outlet in thelower portion of said combustion chamber for the continuous discharge ofmolten slag, and means for introducing a combustion air andparticle-form solid fuel in suspension into said combustion chambertangentially to an imaginary horizontally disposed cylinder in saidcombustion chamber and effecting a whirling path of fuel-air traveltherein along andin sweeping relation with substantially the entireinner surfaces of the walls of said combustion chamber and the slagoutlet thereof to cause continuous discharge of some of the gasesthrough the gas outlet and recirculation of some of the gases in thewhirling path to enhance the ignition of the incoming fuel. a

6. In a fluid heating unit, in combination, wall means defining avertically elongated furnace having an upper radiant chamber and a lowerhorizontally elongated combustion chamber of generally symmetricaltransverse cross-section about its longitudinal axis, the portion of thewall means defining said combustion chamber having an inner exposedrefractory surface and, fluid heating tubes proportioned for themaintenance of said refractory surface under a normal mean temperaturein said combustion chamber above the fuel ash fusion temperature, meansforming a longitudinally extending greatly restricted slot-like gasoutlet in the upper portion of said combustion chamber dividing saidfurnace into said combustion and radiant chambers, said gas outlet beingproportioned so that a predominant portion of the radiant heat energyemitted within said combustion chamber will be absorbed therein and thatthe pressure drop of the gases flowing through said outlet will besufficient to assure uniform distribution of the gases along the wallsof the combustion chamber, means forming a restricted slag outlet in thelower portion of said combustion chamber for the continuous discharge ofmolten slag, and means for introducing combustion air and particle-formsolid fuel in supension into the upper portion of said combustionchamber tangentially to an imaginary horizontally disposed cylinder insaid combustion chamber and effecting a whirling path of fuel-air traveltherein along and in sweeping relation with substantially the entireinner surfaces of the walls of said combustion chamber and the slagoutlet thereof to cause continuous discharge of some of the gasesthrough the gas outlet and recirculation of some of the gases in thewirling path to enhance the ignition of the incoming fuel, said lastnamed means including a series of longitudinally spaced fuel inletsdisposed at one side of and adjacent to said gas outlet, and addi- 7tional air inlets arranged to direct air streams into said combustionchamber tangent to said imaginary cylinder at positions downstream fromsaid fuel inlets and in directions promoting the whirling motion of theburning fuel-air mixture. 7

7. In a fluid heating unit havinga natural circulation fluid circulationsystem, in combination, wall means defining a vertically elongatedfurnace having an upper radiant chamber and a lower horizontallyelongated combustion chamber of generally symmetrical transversecross-section about its longitudinal axis, the portion of the wall meansdefining said combustion chamber having an inner exposed refractorysurface and fluid heating tubes proportioned for the maintenance of saidrefractory surface under a normal mean temperature in said combustionchamber above the fuel ash fusion temperature, said Wall means includingfluid heating tubes extending uninterruptedly upwardly to conform to thecontour of said combustion chamber and said radiant chamber, meansconnecting said fiuid cooled tubes into said fluid circulation system,means forming a longitudinally extending greatly restricted slot-likegas outlet in the upper portion of said combustion chamber dividing saidfurnace into said combustion and radiant chambers, said gas outlet beingproportioned so that a predominant portion of the radiant heat energyemitted within said combustion chamber will be absorbed therein and thatthe pressure drop of the gases flowing through said outlet will besuflicient to assure uniform distribution of the gases along the wallsof the combustion chamber, and means for introducing combustion air andparticle form solid fuel in suspension into said combustion chambertangentially to an imaginary horizontally disposed cylinder in saidcombustion chamher and effecting a whirling path of fuel-air traveltherein along and in sweeping relation with substantially the entireinner surfaces of the walls of said combustion chamber and the slagoutlet thereof to cause continuous discharge of some of the gasesthrough the gas outlet and recirculation of some of the gases in thewhirling path to enhance the i nition of the incoming fuel.

8. Apparatus for burning particle-form solid fuel comprising wall meansforming an elongated combustion chamber of generally symmetricaltransverse cross-section arranged with its longitudinal axissubstantially horizontal, said wall means having an inner exposedrefractory surface and fluid heating tubes proportioned for themaintenance of said refractory surface under a normal mean .temperaturein said combustion chamber above the fuel ash fusion temperature, meansforming a longitudinally extending greatly restricted slot-like gasoutlet in the upper portion of said combustion chamber, said gas outletbeing proportioned so that a predominant portion of the radiant heatenergy emitted within said combustion chamher will be absorbed thereinand that the pressure drop of the gases flowing through said outlet willbe sufiicient to assure uniform distribution of the gases along thewalls of the combustion chamber, means forming a restricted slagoutletin the lower portion of said combustion chamher for the continuousdischarge of molten slag, and means for introducing combustion air andparticle-form solid fuel in suspension into the upper portionof saidcombustion chamber tangentially to an imaginary horizontally disposedcylinder in said combustion chamber and effecting a whirling path offuel-air travel therein along and in sweeping relation withsubstantially the entire inner surfaces of the walls of said combustionchamber and the slag outlet thereof to cause continuous discharge ofsomeof the gases through the gas outlet and recirculation of some ofthegases in the wirling path to enhance the ignition of the incomingfuel, said last named means including a series of longitudinally spacedfuel inlets disposed at one side of and adjacent to said gas outlet,said wall means including lower wall portions terminating downwardly atdifferent elevations at opposite sides of said slag outlet, with theterminal wall portion at the higher-elevation being disposed'upstreamwith respect to the movement of the burning fuel-air mixture.

9; Apparatus for burning particle-form solid fuel comprising wall meansforming an elongated combustion chamber of generally symmetricaltransverse cross-section arranged with its longitudinal axissubstantially horizontal, said wall means including an inner exposedrefractory surface and fluid heating tubes proportioned for themaintenance of said refractory surface under a normal mean temperaturein said combustion chamber above the fuel ash fusion temperature, meansforming a longitudinally extending greatly restricted slot-like gasoutlet in the upper portion of said combustion chamber, said gas outletbeing proportioned so that a predominant portion of the radiant heatenergy emitted within said combustion chamber will be absorbed thereinand that the pressure drop of the gases flowing through said outlet willbe suflicient to assure uniform distribution of the gases along thewalls of the combustion chamber, means form- .ing a restricted slagoutlet in the lower portion of said combustion chamber for thecontinuous discharge of molten slag, means-for introducing combustionand air particle-form solid fuel in suspension into said combustionchamber tangentially to an imaginary horizontally disposed cylinderdisposed in said combustion chamber and effecting a whirling path offuel-air travel therein along and in sweeping relation withsubstantially the entire inner surfaces of the walls of said combustionchamber to cause continuous discharge of some of the gases through thegas outlet and recirculation of some of the gases in the whirling pathto enhance the ignition of the incomingfuel, and means includingportions of said fluid heating tubes and refractory materialco-operating to define longitudinally spaced tube panels extendingacross the narrow part of said gas outlet.

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